1. Field of the Invention
The present invention relates to large displacement flexure stages. More particularly, to flexure-based translation stages that move objects within a plane.
2. Description of the Relevant Art
In general, translation stages (e.g., X-Y stages) are made of actuation components and load-carrying components. When large (e.g., greater than 1 mm) motion ranges are required, lead screw assembly mechanisms have been widely used where positioning accuracy is not a significant factor. For high accuracy applications, ball screw assemblies are used for both actuating and load-carrying components. Backlash and stiction problems are not completely eliminated which are major drawbacks for the ball screw system. Further, the need for lubrication makes it undesirable for vacuum or particle-sensitive applications.
A commonly used high precision X-Y stage is a combination of friction-drive and air bearing mechanisms such as those used in lithography steppers. Two problems, however, may hinder such an X-Y stage from being implemented in more advanced semi-conductor manufacturing equipment, such as vacuum compatible equipment. First, it is difficult to use air bearings inside a vacuum chamber. Second, the problem of possible mechanical failure of the air bearing and friction-driven mechanism exists. Thus, extensive effort and time may be required to maintain the mechanism clean and, if necessary, to replace the mechanism in case of failure.
Magnetically levitated stages were introduced to solve all the problems discussed above. By controlling magnetic fields, a substrate can be accurately positioned or oriented. Through various experiments, positioning accuracy of magnetically levitated stages has been proven to be sufficient for most advanced equipment. Some magnetically levitated stage designs use classical bearing or air bearings to support the weight of the moving body while the magnetic actuators are used only for actuation.
Other designs use magnetic fields as both the actuation and load-carrying systems. In this case, due to the non-linearity of the magnetic fields, accurate control of a magnetically levitated stage has been a challenging task for systems with high degrees of freedom. Only a few cases of practical implementations of magnetically levitated stages were published since its introduction to the lithography industry. The overall cost of magnetically levitated stages is expected to be much higher than conventional mechanical designs.